1. Field of the Invention
This invention pertains to the fields of tomography and pneumoencephalography, and more specifically to patient supporting apparatus for making tomograms during pneumoencephalography.
2. Description of the Prior Art
Pneumoencephalography is a medical procedure for determining the size and location of brain tumors. A tumor in the brain normally distorts the shape of the ventricles or cavities in the brain. Accordingly, a picture of the exact shape of the ventricles would indirectly reveal to a great extent the size and location of any major tumor. Unfortunatley the ventricles are normally filled with cerebral fluid, which absorbs x-rays about as well as brain tissue, so that the ventricles cannot ordinarily be x-rayed well even with tomography. Tomography is an x-ray technique whereby the x-ray source and film are moved about during exposure in a fashion so that only one plane through the body or object is clearly seen and other planes are blurred and not distinctly seen. In pneumoencephalography a small amount of air is injected into the spinal column of an erect patient so that it travels up the spinal column and into the ventricles where it displaces some of the cerebral fluid in the ventricles. The difference is sufficient between the x-ray absorption of brain tissue and of air to then make tomographic x-ray exposures showing the shape of the air bubble, which corresponds to the shape of the ventricles bounding the air bubble. Ordinarily a series of many exposures is made during which the patient is positioned in different orientations with respect to gravity so that the air bubble moves around to different ventricles and to different sides of the same ventricles.
Prior art apparatus for carrying out this method includes a patient supporting apparatus that is capable of moving the patient into the many required positions. Once the patient has been properly positioned with respect to gravity and the bubble is theoretically at a desired location, the supporting apparatus and patient are positioned with respect to a tomography machine so that one or more tomograms of the brain can be made with the patient and bubble in that position. Thereafter, the patient is repositioned and the supporting apparatus and patient are again positioned with respect to the tomography machine for more tomograms of the brain. Because the patient's head must be positioned very close to the tomography table and at a fairly precise location, in prior art apparatus, the patient must be moved at least slightly away from the table for repositioning because the table would otherwise interfere with the repositioning. After the patient is repositioned, his head must then again be brought very close to the tomography table and to a fairly precise location. It should be appreciated that at least six, preferably nine, and possibly as many as twelve or more patient positions are required and that each time the head must be accurately positioned with respect to the tomography machine. Prior art supporting apparatus obviously has means for making accurate position adjustment, but the procedure is time consuming and prone to error due to the large number of required accurate positionings. Pneumoencephalography is a very traumatic and painful experience for the patient, so that repetition of the study is very undesirable. Since the entire procedure is also very time consuming, taking several or more hours, any reduction in time required for the procedure is also very desirable.